Process of producing light-colored tanned leather



Patented Jan. 13, 1925.

UNITED STATES OSCAR LO'W' BEER,OF FRANKFORT-ON-THE-MAIN, GERMANY.

PROCESS OF PRODUCING LIGHT-COLORED TANNED LEATHER.

No Drawing.

To all whom it may concern:

Be it known that I, OSCAR Low BEER, a citizen of Czechoslovakia, residing at Frankfort-on-the-Main, Prussia, Germany,-

have invented certain new and useful Improvements in Processes of Producing Light-Colored Tanned Leather, of which the following is a specification.

A large part of the hides and skins obtained from abroad, for instance, from India, the Orient and South America are halftanned or bark-tanned and have a more or less brownish or reddish color and also show in other respects the properties of vegetable-tanned leather, which, as is well known, has a number of objectionable characteristics, especially in its use for the manufacture of uppers and leather novelties.

In order to make these hides suitable for the preparation of uppers and leather novelties, it is customary to bleach them with sumach, but the productso obtained is unfit for a variety of uses due to the fact that it is of too dark a shade and possesses a certain stiffness.

The East Indian hides have heretofore been used only in split or unsplit form for the production of cheap uppers or insoles or, after removing apart of the vegetable tanning material from them by a tedious method, to prepare them for tanning with chromium salts.

It has now been found that by bleaching the above mentioned hides and skins with aluminum and chromium compounds of synthetic tanning agents and more particularly the aluminum and chromium salts of synthetic tanning agents comprising two aromatic sulfo acids linked together, leather of a light, almost white, color suitable for all uses and capable of being colored the most delicate tints can be produced. The product is full, soft and pliable. The treatment of East Indian kid leather or lamb skins with chromium salts of synthetic tanning agents gives a good chevreau-like leather. East Indian tanned leather or hemlock leather treated in the same manner with chromium compounds of synthetic tanning agents, after suit-able finishing or dressing, has a surface of a typically chrome-tanned character. The red color of hemlock leather disappears completely and a bright colored leather suitable for the most varied uses is produced. Indian half- Application filed March 13, 1924. Serial No. 699.077.

tanned kid leather and lamb skins are treated as follows (1) The well softened leather is worked for about 6 hours in a bath of an aluminum or chromium compound of a synthetic tanning agent of about 3 Be and then allowed to drain over night and then worked again for about 10 minutes in pure ironfree water, and then finished in the usual way. In this way a very light colored leather suitable for use in the shoe and pocket-book trades and having a chevreaulike character is obtained.

(2) East Indian tanned or hemlock leather is treated win the chromium compounds of synthetic tann ng agents as follows e T The hides and splits are treated for about 10 hours in a 3 to 5 B. '"-lution and then allowed to drain for about 24 hours and then worked for about 10- minutes in pure water and then finished in the usual way.

The solutions of the aluminum and chromium compounds of synthetic tanning agents can be used over and over again for the treatment of successive batches of hides by restoring the strength thereof from time to timeas is necessary by the addition of fresh tanning material.

.The process of the present invention of course is applicable to bark-tanned or vegetable-tanned leather of all kinds and from all sources and is not to be understood as being limited to the treatment of such leather produced in any particular locality.

Examples of chromium and aluminum compounds of synthetic tanning agents suitable for use in accordance with my invention are disclosed in French Patent No. 530,371 and British Patents Nos. 148,126; 154,153; 156,254 and 133,749, in which are disclosed for instance chromium and aluminum salts of compounds formed by linking together two aromatic sulfo acids by means of a condensing agent such as formaldehyde.

The metals, aluminum and chromium are generally associated, due to the similarity of the properties of their compounds, in the tanning art and they are therefore designated generically in the appended claims as tanning metals.

Claims:

1. Process of producing light colored tanned leather by converting vegetabletanned leather into leather having a chrome-tanned character which comprises treating the vegetable-tanned leather with a tanning metal salt of a compound comprising tWo aromatic sulfo acids linked together.

2. Process of producing light colored-- tanned leather by. converting vegetabletanned leather into leather having a chrome-tanned character. which comprises treating the vegetable-tanned leather with 10 a chromium salt of a synthetic tanning agent.

In testimony whereof, I aflix my signature.

OSCAR LOW BEER. Witnesses:

GABRIELE FLnscH, JANE Gmsrr. 

